Sugars phenylhydrazine

Hydrazine and its alkylated derivatives are used as rocket fuels in organic chemistry, substituted phenylhydrazines are important in the characterisation of sugars and other compounds, for example aldehydes and ketones containing the carbonyl group C=0. 

Another reaction that is characteristic of a-hydroxy aldehydes or ketones, which has been found of value for the characterisation of sugars, is the formation of osazones with phenylhydrazine. This reagent reacts with either an aldose... 

Simple sugars undergo reaction with phenylhydrazine, PhNHNH2, to yield crystalline derivatives called osazones. The reaction is a bit complex, however, as shown by the fact that glucose and fructose yield the same osazone. 

Reducing sugars can be detected by reaction with phenylhydrazine to yield a hydrazone product, except the result of the reaction is not what one might imagine giving the structure of aldoses and ketoses. Glucose, for example, can react with phenylhydrazine to yield the anticipated... 

Sugar lactones react readily with hydrazine to give crystalline derivatives useful for isolation and identification (127). Thus, addition of hydrazine to a reaction mixture containing an aldonolactone facilitates isolation of the product. The lactone may be regenerated from the hydrazide by treatment with nitrous acid (128). The phenylhydrazides obtained on treatment of aldonolactones with phenylhydrazine are also useful for characterization (129,130). 

In sugar chemistry phenylhydrazine has become of outstanding importance for the separation, characterisation, and transformation of the various kinds of sugars. The fundamental results of this domain could hardly have been obtained without this reagent. When one molecule of a sugar reacts with one molecule of phenylhydrazine a normal hydra-zone is formed, e.g. 

Like all hydrazones, osazones lose phenylhydrazine when heated with hydrochloric acid. Naturally, it is not the sugar originally taken which is thus recovered, but an oxidation product, a so-called osone. In the example chosen the osone is ... 

The flavazoles, an interesting type of pyrazoline derivative obtained by interacting sugar quinoxalines with phenylhydrazine, will be discussed in the next Section (see p. 398). 

Reaction (reduction) with phenylhydrazine (osazone test) The open chain form of the sugar reacts with phenylhydrazine to produce a pheny-losazone. Three moles of phenylhydrazine are used, but only two moles taken up at C-1 and C-2. 

Pentoses and hexoaes could be distinguished readily with phenylhydra-zine. The compound hitherto called isodulcitol was identified as a sugar by means of phenylhydrazine, and was designated as rhamnose from that time on. Glucose and fructose (which H. Kiliani had discerned to be an aldohexose and a ketohexose, respectively) and mannose were found to give one and the same phenylosazone the three sugars, therefore, have the same configuration at carbon atoms 3, 4, and 5. 

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